Myriad devices operate by converting rotational motion into linear motion. In one example, an actuator may be used to rotate a shaft that is coupled to a stem of a component. The component may be part of a gate valve, poppet valve, or any other similar device where rotational motion of the stem moves a body linearly between a first position and a second position. To maintain the stem and the actuator shaft axially aligned with each other, both may extend through a passage in a carrier. The passage may also house a drive nut having an inner surface shaped to correspond with a shape of an outer surface of the stem. Thus, when the shaft rotates the stem, the stem is guided along a linear path through the carrier via the drive nut.
Although the above-described device generally operates adequately, it may be improved. In particular, in some cases, the drive nut may become displaced within the carrier. As a result, the stem may become misaligned relative to the actuator shaft, and the device may not operate as desired. In some cases, a bearing assembly may be mounted on an outer surface of the carrier to allow the device to operate despite the misalignment between the actuator shaft and the stem. However, prolonged misalignment between the shaft and the stem may cause the carrier to apply excessive radial forces against bearings of the bearing assembly and/or may cause an undesirable side load against the carrier. Consequently, performance of the device may be affected.
Hence, it is desirable to provide a mechanism for coupling a stem to an actuator that allows the stem and the actuator to operate despite misalignment therebetween. It is also desirable for the mechanism to compensate for the aforementioned misalignment without applying unwanted radial forces and/or side loads against the actuator, the stem, and/or surrounding components. Moreover, it is desirable for the mechanism to be simple to implement into existing devices.